Communication techniques using visible light have been proposed. For example, as in Patent Literatures (PTLs) 1 and 2, there are proposals on video display devices such as displays and projectors, to superimpose visible light communication information onto a normal video to be displayed, and display the resulting video.
In addition, there are digital watermark technology which is in pilot use in printed materials and techniques for displaying, in images, QR codes (registered trademark), bar codes, or the like, and using coded signals thereof to spread information to the Internet world through imaging devices such as mobile phones, smartphones, and digital cameras.